Capacitive sensing using non-integer excitation

ABSTRACT

Capacitive sensing includes concurrently driving a first transmitter electrode with a first transmitter signal and a second transmitter electrode with a second transmitter signal. The first transmitter signal is based on a first digital code and the second transmitter signal is based on a second digital code. The first digital code and the second digital code each include at least one non-integer multiple. Capacitive sensing further includes receiving resulting signals using multiple receiver electrodes, the resulting signals include effects of the first transmitter signal and the second transmitter signal. Capacitive sensing further includes determining positional information based on the resulting signals.

FIELD

This invention generally relates to electronic devices.

BACKGROUND

Input devices, including proximity sensor devices (also commonly calledtouchpads or touch sensor devices), are widely used in a variety ofelectronic systems. A proximity sensor device typically includes asensing region, often demarked by a surface, in which the proximitysensor device determines the presence, location and/or motion of one ormore input objects. Proximity sensor devices may be used to provideinterfaces for the electronic system. For example, proximity sensordevices are often used as input devices for larger computing systems(such as opaque touchpads integrated in, or peripheral to, notebook ordesktop computers). Proximity sensor devices are also often used insmaller computing systems (such as touch screens integrated in cellularphones).

SUMMARY

In general, in one aspect, one or more embodiments relate to acapacitive sensing device including a first transmitter electrode, asecond transmitter electrode, and multiple receiver electrodes, and aprocessing system. The processing system is configured to concurrentlydrive a first transmitter electrode with a first transmitter signal anda second transmitter electrode with a second transmitter signal. Thefirst transmitter signal is based on a first digital code and the secondtransmitter signal is based on a second digital code. The first digitalcode and the second digital code each include at least one non-integermultiple. The processing system is further configured to receivemultiple resulting signals using multiple receiver electrodes, theresulting signals including effects of the first transmitter signal andthe second transmitter signal, and determine positional informationbased on the resulting signal.

In general, in one aspect, one or more embodiments relate to a methodfor capacitive sensing that includes concurrently driving a firsttransmitter electrode with a first transmitter signal and a secondtransmitter electrode with a second transmitter signal. The firsttransmitter signal is based on a first digital code and the secondtransmitter signal is based on a second digital code. The first digitalcode and the second digital code each include at least one non-integermultiple. The method further includes receiving resulting signals usingmultiple receiver electrodes, the resulting signals include effects ofthe first transmitter signal and the second transmitter signal. Themethod further includes determining positional information based on theresulting signals.

In general, in one aspect, one or more embodiments relate to processingsystem for capacitive sensing that includes sensor circuitry configuredto concurrently drive a first transmitter electrode with a firsttransmitter signal and a second transmitter electrode with a secondtransmitter signal. The first transmitter signal is based on a firstdigital code and the second transmitter signal is based on a seconddigital code. The first digital code and the second digital code eachinclude at least one non-integer multiple. The sensor circuitry isfurther configured to receive resulting signals using multiple receiverelectrodes. The resulting signals include effects of the firsttransmitter signal and the second transmitter signal. The processingsystem further includes processing circuitry configured to determinepositional information based on the plurality of resulting signals.

Other aspects of the invention will be apparent from the followingdescription and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

The preferred exemplary embodiment of the present invention willhereinafter be described in conjunction with the appended drawings,where like designations denote like elements, and:

FIGS. 1, 2.1, and 2.2 show schematic diagrams in accordance with one ormore embodiments of the invention.

FIG. 3 shows an example in accordance with one or more embodiments ofthe invention.

FIG. 4 shows a flowchart in accordance with one or more embodiments ofthe invention.

DETAILED DESCRIPTION

The following detailed description is merely exemplary in nature, and isnot intended to limit the invention or the application and uses of theinvention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, brief summary or the following detailed description.

In the following detailed description of embodiments of the invention,numerous specific details are set forth in order to provide a morethorough understanding of the invention. However, it will be apparent toone of ordinary skill in the art that the invention may be practicedwithout these specific details. In other instances, well-known featureshave not been described in detail to avoid unnecessarily complicatingthe description.

Throughout the application, ordinal numbers (e.g., first, second, third,etc.) may be used as an adjective for an element (i.e., any noun in theapplication). The use of ordinal numbers is not to imply or create anyparticular ordering of the elements nor to limit any element to beingonly a single element unless expressly disclosed, such as by the use ofthe terms “before”, “after”, “single”, and other such terminology.Rather, the use of ordinal numbers is to distinguish between theelements. By way of an example, a first element is distinct from asecond element, and the first element may encompass more than oneelement and succeed (or precede) the second element in an ordering ofelements.

Various embodiments of the present invention provide input devices andmethods that facilitate improved usability. In particular, one or moreembodiments are directed to driving multiple transmitter electrodesconcurrently using digital codes that include non-integer multiples. Inone or more embodiments of the invention, the carrier signal ismodulated based on the respective digital code. In one or moreembodiments of the invention, the non-integer multiple codes areorthogonal, and may exhibit a higher signal to noise ratio.

Turning now to the figures, FIG. 1 is a block diagram of an exemplaryinput device (100), in accordance with embodiments of the invention. Theinput device (100) may be configured to provide input to an electronicsystem (not shown). As used in this document, the term “electronicsystem” (or “electronic device”) broadly refers to any system capable ofelectronically processing information. Some non-limiting examples ofelectronic systems include personal computers of all sizes and shapes,such as desktop computers, laptop computers, netbook computers, tablets,web browsers, e-book readers, and personal digital assistants (PDAs).Additional example electronic systems include composite input devices,such as physical keyboards that include input device (100) and separatejoysticks or key switches. Further example electronic systems includeperipherals, such as data input devices (including remote controls andmice), and data output devices (including display screens and printers).Other examples include remote terminals, kiosks, and video game machines(e.g., video game consoles, portable gaming devices, and the like).Other examples include communication devices (including cellular phones,such as smart phones), and media devices (including recorders, editors,and players such as televisions, set-top boxes, music players, digitalphoto frames, and digital cameras). Additionally, the electronic systemcould be a host or a slave to the input device.

The input device (100) may be implemented as a physical part of theelectronic system, or may be physically separate from the electronicsystem. Further, portions of the input device (100) may be part of theelectronic system. For example, all or part of the processing system maybe implemented in the device driver of the electronic system. Asappropriate, the input device (100) may communicate with parts of theelectronic system using any one or more of the following: buses,networks, and other wired or wireless interconnections. Examples includeI2C, SPI, PS/2, Universal Serial Bus (USB), Bluetooth, RF, and IRDA.

In FIG. 1, the input device (100) is shown as a proximity sensor device(also often referred to as a “touchpad” or a “touch sensor device”)configured to sense input provided by one or more input objects (140) ina sensing region (120). Example input objects include fingers and styli,as shown in FIG. 1, which may be used together or independently.Throughout the specification, the singular form of input object is used.Although the singular form is used, multiple input objects may exist inthe sensing region (120). Further, which particular input objects are inthe sensing region may change over the course of one or more gestures.To avoid unnecessarily complicating the description, the singular formof input object is used and refers to all of the above variations.

The sensing region (120) encompasses any space above, around, in and/ornear the input device (100) in which the input device (100) is able todetect user input (e.g., user input provided by one or more inputobjects (140)). The sizes, shapes, and locations of particular sensingregions may vary widely from embodiment to embodiment.

In some embodiments, the sensing region (120) extends from a surface ofthe input device (100) in one or more directions into space untilsignal-to-noise ratio (SNR) prevents sufficiently accurate objectdetection. The extension above the surface of the input device may bereferred to as the above surface sensing region. The distance to whichthis sensing region (120) extends in a particular direction, in variousembodiments, may be on the order of less than a millimeter, millimeters,centimeters, or more, and may vary significantly with the type ofsensing technology used and the accuracy desired. Thus, some embodimentssense input that comprises no contact with any surfaces of the inputdevice (100), contact with an input surface (e.g. a touch surface) ofthe input device (100), contact with an input surface of the inputdevice (100) coupled with some amount of applied force or pressure,and/or a combination thereof. In various embodiments, input surfaces maybe provided by surfaces of casings within which the sensor electrodesreside, by face sheets applied over the sensor electrodes or anycasings, etc. In some embodiments, the sensing region (120) has arectangular shape when projected onto an input surface of the inputdevice (100).

The input device (100) may utilize any combination of sensor componentsand sensing technologies to detect user input in the sensing region(120). The input device (100) includes one or more sensing elements fordetecting user input. As several non-limiting examples, the input device(100) may use capacitive, elastive, resistive, inductive, magnetic,acoustic, ultrasonic, and/or optical techniques.

Some implementations are configured to provide images that span one,two, three, or higher-dimensional spaces. Some implementations areconfigured to provide projections of input along particular axes orplanes. Further, some implementations may be configured to provide acombination of one or more images and one or more projections.

In some resistive implementations of the input device (100), a flexibleand conductive first layer is separated by one or more spacer elementsfrom a conductive second layer. During operation, one or more voltagegradients are created across the layers. Pressing the flexible firstlayer may deflect it sufficiently to create electrical contact betweenthe layers, resulting in voltage outputs reflective of the point(s) ofcontact between the layers. These voltage outputs may be used todetermine positional information.

In some inductive implementations of the input device (100), one or moresensing elements pick up loop currents induced by a resonating coil orpair of coils. Some combination of the magnitude, phase, and frequencyof the currents may then be used to determine positional information.

In some capacitive implementations of the input device (100), voltage orcurrent is applied to create an electric field. Nearby input objectscause changes in the electric field, and produce detectable changes incapacitive coupling that may be detected as changes in voltage, current,or the like.

Some capacitive implementations utilize arrays or other regular orirregular patterns of capacitive sensing elements to create electricfields. In some capacitive implementations, separate sensing elementsmay be ohmically shorted together to form larger sensor electrodes. Somecapacitive implementations utilize resistive sheets, which may beuniformly resistive.

Some capacitive implementations utilize “self capacitance” (or “absolutecapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes and an input object. In variousembodiments, an input object near the sensor electrodes alters theelectric field near the sensor electrodes, thus changing the measuredcapacitive coupling. In one implementation, an absolute capacitancesensing method operates by modulating sensor electrodes with respect toa reference voltage (e.g., system ground), and by detecting thecapacitive coupling between the sensor electrodes and input objects. Thereference voltage may be a substantially constant voltage or a varyingvoltage and in various embodiments; the reference voltage may be systemground. Measurements acquired using absolute capacitance sensing methodsmay be referred to as absolute capacitive measurements.

Some capacitive implementations utilize “mutual capacitance” (or “transcapacitance”) sensing methods based on changes in the capacitivecoupling between sensor electrodes. In various embodiments, an inputobject near the sensor electrodes alters the electric field between thesensor electrodes, thus changing the measured capacitive coupling. Inone implementation, a mutual capacitance sensing method operates bydetecting the capacitive coupling between one or more transmitter sensorelectrodes (also “transmitter electrodes” or “transmitter”) and one ormore receiver sensor electrodes (also “receiver electrodes” or“receiver”). Transmitter sensor electrodes may be modulated relative toa reference voltage (e.g., system ground) to transmit transmittersignals. Receiver sensor electrodes may be held substantially constantrelative to the reference voltage to facilitate receipt of resultingsignals. The reference voltage may be a substantially constant voltageand in various embodiments; the reference voltage may be system ground.In some embodiments, transmitter sensor electrodes may both bemodulated. The transmitter electrodes are modulated relative to thereceiver electrodes to transmit transmitter signals and to facilitatereceipt of resulting signals. A resulting signal may include effect(s)corresponding to one or more transmitter signals, and/or to one or moresources of environmental interference (e.g., other electromagneticsignals). The effect(s) may be the transmitter signal, a change in thetransmitter signal caused by one or more input objects and/orenvironmental interference, or other such effects. Sensor electrodes maybe dedicated transmitters or receivers, or may be configured to bothtransmit and receive. Measurements acquired using mutual capacitancesensing methods may be referred to as mutual capacitance measurements.

Further, the sensor electrodes may be of varying shapes and/or sizes.The same shapes and/or sizes of sensor electrodes may or may not be inthe same groups. For example, in some embodiments, receiver electrodesmay be of the same shapes and/or sizes while, in other embodiments,receiver electrodes may be varying shapes and/or sizes. By way ofanother example, in some embodiments, transmitter electrodes may be ofthe same shapes and/or sizes while, in other embodiments, transmitterelectrodes may be varying shapes and/or sizes.

In other embodiments, one or more of sensor electrodes are disposed onthe same side or surface of the common substrate and are isolated fromeach other in the sensing region. The sensor electrodes may be disposedin a matrix array where each sensor electrode may be referred to as amatrix sensor electrode. The matrix array may correspond to a gridpattern. Each sensor electrode of sensor electrodes may be substantiallysimilar in size and/or shape. In one embodiment, one or more of thesensor electrodes of the matrix array of sensor electrodes may vary inat least one of the size and shape. Each sensor electrode of the matrixarray may correspond to a pixel of a capacitive image (i.e., capacitivepixel). Further, two or more sensor electrodes of the matrix array maycorrespond to a pixel of a capacitive image (i.e., capacitive pixel). Inother words, a capacitive pixel is a location at which a measurement isacquired. In various embodiments, each sensor electrode of the matrixarray may be coupled to a separate capacitive routing trace of aplurality of capacitive routing traces. In various embodiments, thesensor electrodes include one or more gird electrodes disposed betweenat least two sensor electrodes of the sensor electrodes. The gridelectrode and at least one sensor electrode may be disposed on a commonside of a substrate, different sides of a common substrate and/or ondifferent substrates. In one or more embodiments, the sensor electrodesand the grid electrode(s) may encompass an entire voltage electrode of adisplay device. Although the sensor electrodes may be electricallyisolated on the substrate, the electrodes may be coupled togetheroutside of the sensing region (e.g., in a connection region). In one ormore embodiments, a floating electrode may be disposed between the gridelectrode and the sensor electrodes. In one particular embodiment, thefloating electrode, the grid electrode and the sensor electrode includethe entirety of a common electrode of a display device.

In any sensor electrode arrangement (e.g., the matrix array describedabove), the sensor electrodes may be operated by the input device formutual capacitive sensing by dividing the sensor electrodes intotransmitter and receiver electrodes. As another example, in any sensorelectrode arrangement (e.g., the matrix array described above), thesensor electrodes may be operated by the input device for absolutecapacitive sensing. As another example, in any sensor electrodearrangement, a mixture of absolute and mutual capacitance sensing may beused. Further, one or more of the sensor electrodes or the displayelectrodes (e.g., source, gate, or reference (Vcom) electrodes) may beused to perform shielding.

A set of measurements from the capacitive pixels form a capacitiveframe. In other words, the capacitive frame represents the set ofmeasurements acquired for a moment in time. The measurements includeeffects of the capacitance, an input object in the sensing region, andany background capacitance. The capacitive frame may include acapacitive image that is representative of the capacitive couplings atthe pixels and/or include a capacitive profile that is representative ofthe capacitive couplings or along each sensor electrode. Multiplecapacitive frames may be acquired over multiple time periods, anddifferences between them may be used to derive information about inputin the sensing region. For example, successive capacitive framesacquired over successive periods of time can be used to track themotion(s) of one or more input objects entering, exiting, and within thesensing region.

The background capacitance of a sensor device is the capacitive frameassociated with no input object in the sensing region. The backgroundcapacitance changes with the environment and operating conditions, andmay be estimated in various ways. For example, some embodiments take“baseline frames” when no input object is determined to be in thesensing region, and use those baseline frames as estimates of theirbackground capacitances. The baseline frame is a capacitive frameobtained using capacitive sensing when an input object is not in thesensing region.

Capacitive frames can be adjusted for the background capacitance of thesensor device for more efficient processing. Some embodiments accomplishthis by “baselining” measurements of the capacitive couplings at thecapacitive pixels to produce “baselined capacitive frames.” That is,some embodiments compare the measurements forming capacitance frameswith corresponding “baseline values” of “baseline frames”, and determinechanges from that baseline image.

In FIG. 1, a processing system (110) is shown as part of the inputdevice (100). The processing system (110) is configured to operate thehardware of the input device (100) to detect input in the sensing region(120). The processing system (110) includes parts of, or all of, one ormore integrated circuits (ICs) and/or other circuitry components. Forexample, a processing system for a mutual capacitance sensor device mayinclude transmitter circuitry configured to transmit signals withtransmitter sensor electrodes, and/or receiver circuitry configured toreceive signals with receiver sensor electrodes. Further, a processingsystem for an absolute capacitance sensor device may include drivercircuitry configured to drive absolute capacitance signals onto sensorelectrodes, and/or receiver circuitry configured to receive signals withthose sensor electrodes. In one or more embodiments, a processing systemfor a combined mutual and absolute capacitance sensor device may includeany combination of the above described mutual and absolute capacitancecircuitry. In some embodiments, the processing system (110) alsoincludes electronically-readable instructions, such as firmware code,software code, and/or the like. In some embodiments, componentscomposing the processing system (110) are located together, such as nearsensing element(s) of the input device (100). In other embodiments,components of processing system (110) are physically separate with oneor more components close to the sensing element(s) of the input device(100), and one or more components elsewhere. For example, the inputdevice (100) may be a peripheral coupled to a computing device, and theprocessing system (110) may include software configured to run on acentral processing unit of the computing device and one or more ICs(perhaps with associated firmware) separate from the central processingunit. As another example, the input device (100) may be physicallyintegrated in a mobile device, and the processing system (110) mayinclude circuits and firmware that are part of a main processor of themobile device. In some embodiments, the processing system (110) isdedicated to implementing the input device (100). In other embodiments,the processing system (110) also performs other functions, such asoperating display screens, driving haptic actuators, etc.

The processing system (110) may be implemented as a set of modules thathandle different functions of the processing system (110). Each modulemay include circuitry that is a part of the processing system (110),firmware, software, or a combination thereof. In various embodiments,different combinations of modules may be used. For example, as shown inFIG. 1, the processing system (110) may include processing circuitry(150) and sensor circuitry (160). The processing circuitry (150) maycorrespond to hardware circuitry, such as a central processing unit, anapplication specific integrated circuit, or other hardware. Theprocessing circuitry (150) may include functionality to detect apresence of moisture, operate based on the presence of moisture,determine when at least one input object is in a sensing region,determine SNR, determine positional information of an input object,identify a gesture, determine an action to perform based on the gesture,a combination of gestures or other information, perform otheroperations, and/or perform any combination of operations.

The sensor circuitry (160) may correspond to hardware circuitry, such asa central processing unit, an application specific integrated circuit,or other hardware that includes functionality to drive the sensorelectrodes. For example, the sensor module (160) may include sensorycircuitry that is coupled to the sensing elements.

Although FIG. 1 shows the processing circuitry (150) and the sensorcircuitry (160) as separate components, all or part of the processingcircuitry (150) may be the same as the sensor circuitry (160). Further,although FIG. 1 shows only processing circuitry (150) and sensorcircuitry (160), alternative or additional hardware circuitry may existin accordance with one or more embodiments of the invention. Suchalternative or additional circuitry may correspond to distinct circuitryor sub-circuitry than one or more of the circuitry discussed above.Example alternative or additional circuitry includes hardware operationcircuitry for operating hardware such as sensor electrodes and displayscreens, data processing circuitry for processing data such as sensorsignals and positional information, reporting circuitry for reportinginformation, and identification circuitry configured to identifygestures, such as mode changing gestures, and mode changing circuitryfor changing operation modes. Further, the various circuitries may becombined in separate integrated circuits. For example, a first circuitrymay be comprised at least partially within a first integrated circuit,and a separate circuitry may be comprised at least partially within asecond integrated circuit. Further, portions of a single circuitry mayspan multiple integrated circuits. In some embodiments, the processingsystem as a whole may perform the operations of the various circuitries.

In some embodiments, the processing system (110) responds to user input(or lack of user input) in the sensing region (120) directly by causingone or more actions. Example actions include changing operation modes,as well as graphical user interface (GUI) actions such as cursormovement, selection, menu navigation, and other functions. In someembodiments, the processing system (110) provides information about theinput (or lack of input) to some part of the electronic system (e.g. toa central processing system of the electronic system that is separatefrom the processing system (110), if such a separate central processingsystem exists). In some embodiments, some part of the electronic systemprocesses information received from the processing system (110) to acton user input, such as to facilitate a full range of actions, includingmode changing actions and GUI actions.

For example, in some embodiments, the processing system (110) operatesthe sensing element(s) of the input device (100) to produce electricalsignals indicative of input (or lack of input) in the sensing region(120). The processing system (110) may perform any appropriate amount ofprocessing on the electrical signals in producing the informationprovided to the electronic system. For example, the processing system(110) may digitize analog electrical signals obtained from the sensorelectrodes. As another example, the processing system (110) may performfiltering or other signal conditioning. As yet another example, theprocessing system (110) may subtract or otherwise account for abaseline, such that the information reflects a difference between theelectrical signals and the baseline. As yet further examples, theprocessing system (110) may determine positional information, recognizeinputs as commands, recognize handwriting, and the like.

“Positional information” as used herein broadly encompasses absoluteposition, relative position, velocity, acceleration, and other types ofspatial information. Exemplary “zero-dimensional” positional informationincludes near/far or contact/no contact information. Exemplary“one-dimensional” positional information includes positions along anaxis. Exemplary “two-dimensional” positional information includesmotions in a plane. Exemplary “three-dimensional” positional informationincludes instantaneous or average velocities in space. Further examplesinclude other representations of spatial information. Historical dataregarding one or more types of positional information may also bedetermined and/or stored, including, for example, historical data thattracks position, motion, or instantaneous velocity over time.

In some embodiments, the input device (100) is implemented withadditional input components that are operated by the processing system(110) or by some other processing system. These additional inputcomponents may provide redundant functionality for input in the sensingregion (120), or some other functionality. FIG. 1 shows buttons (130)near the sensing region (120) that may be used to facilitate selectionof items using the input device (100). Other types of additional inputcomponents include sliders, balls, wheels, switches, and the like.Conversely, in some embodiments, the input device (100) may beimplemented with no other input components.

In some embodiments, the input device (100) includes a touch screeninterface, and the sensing region (120) overlaps at least part of anactive area of a display screen. For example, the input device (100) mayinclude substantially transparent sensor electrodes overlaying thedisplay screen and provide a touch screen interface for the associatedelectronic system. The display screen may be any type of dynamic displaycapable of displaying a visual interface to a user, and may include anytype of light emitting diode (LED), organic LED (OLED), cathode ray tube(CRT), liquid crystal display (LCD), plasma, electroluminescence (EL),or other display technology. The input device (100) and the displayscreen may share physical elements. For example, some embodiments mayutilize some of the same electrical components for displaying andsensing. In various embodiments, one or more display electrodes of adisplay device may be configured for both display updating and inputsensing. As another example, the display screen may be operated in partor in total by the processing system (110).

In various embodiments, the input device (100) may include one or moresensor electrodes configured for both display updating and inputsensing. For example, at least one sensor electrode that is used forinput sensing may comprise one or more display electrodes of the displaydevice that are used in updating the display. Further, the displayelectrode may include one or more of segments of a Vcom electrode(common electrodes), source drive lines (electrodes), gate line(electrodes), an anode sub-pixel electrode or cathode pixel electrode,or any other display element. These display electrodes may be disposedon an appropriate display screen substrate. For example, the displayelectrodes may be disposed on a transparent substrate (a glasssubstrate, TFT glass, or any other transparent material) in some displayscreens (e.g., In Plane Switching (IPS), Fringe Field Switching (FFS) orPlane to Line Switching (PLS) Organic Light Emitting Diode (OLED)), onthe bottom of the color filter glass of some display screens (e.g.,Patterned Vertical Alignment (PVA) Multi-domain Vertical Alignment(MVA), IPS and FFS), over an cathode layer (OLED), etc. In suchembodiments, the display electrode can also be referred to as a“combination electrode”, since it performs multiple functions. Invarious embodiments, each of the sensor electrodes includes one or moredisplay electrodes associated with a pixel or sub pixel. In otherembodiments, at least two sensor electrodes may share at least onedisplay electrode associated with a pixel or sub-pixel.

In various embodiments, a first sensor electrode includes one or moredisplay electrodes configured for display updating and capacitivesensing and a second sensor electrode may be configured for capacitivesensing and not for display updating. The second sensor electrode may bedisposed between substrates of the display device or external from thedisplay device. In some embodiments, all of the sensor electrodes mayinclude one or more display electrodes configured for display updatingand capacitive sensing.

Processing system (110) may be configured to perform input sensing anddisplay updating during at least partially overlapping periods. Forexample, a processing system (110) may simultaneously drive a firstdisplay electrode for both display updating and input sensing. Inanother example, processing system (110) may simultaneously drive afirst display electrode for display updating and a second displayelectrode for input sensing. In some embodiments, processing system(110) is configured to perform input sensing and display updating duringnon-overlapping periods. The non-overlapping periods may be referred toas non-display update periods. The non-display update periods may occurbetween display line update periods of common display frame and be atleast as long as a display line update period. Further, the non-displayupdate periods may occur between display line update periods of a commondisplay frame and be one of longer than or shorter than a display lineupdate period. In some embodiments, the non-display update periods mayoccur at the beginning of a display frame and/or between display frames.Processing system (110) may be configured to drive one or more of thesensor electrodes and/or the display electrodes with a shield signal.The shield signal may comprise one of a constant voltage signal or avarying voltage signal (guard signal). Further, one or more of thesensor electrodes and/or display electrodes may be electrically floated.

It should be understood that while many embodiments of the invention aredescribed in the context of a fully-functioning apparatus, themechanisms of the present invention are capable of being distributed asa program product (e.g., software) in a variety of forms. For example,the mechanisms of the present invention may be implemented anddistributed as a software program on information-bearing media that arereadable by electronic processors (e.g., non-transitorycomputer-readable and/or recordable/writable information bearing mediathat is readable by the processing system (110)). Additionally, theembodiments of the present invention apply equally regardless of theparticular type of medium used to carry out the distribution. Forexample, software instructions in the form of computer readable programcode to perform embodiments of the invention may be stored, in whole orin part, temporarily or permanently, on a non-transitorycomputer-readable storage medium. Examples of non-transitory,electronically-readable media include various discs, physical memory,memory, memory sticks, memory cards, memory modules, and or any othercomputer readable storage medium. Electronically-readable media may bebased on flash, optical, magnetic, holographic, or any other storagetechnology.

Although not shown in FIG. 1, the processing system, the input device,and/or the host system may include one or more computer processor(s),associated memory (e.g., random access memory (RAM), cache memory, flashmemory, etc.), one or more storage device(s) (e.g., a hard disk, anoptical drive such as a compact disk (CD) drive or digital versatiledisk (DVD) drive, a flash memory stick, etc.), and numerous otherelements and functionalities. The computer processor(s) may be anintegrated circuit for processing instructions. For example, thecomputer processor(s) may be one or more cores or micro-cores of aprocessor. Further, one or more elements of one or more embodiments maybe located at a remote location and connected to the other elements overa network. Further, embodiments of the invention may be implemented on adistributed system having several nodes, where each portion of theinvention may be located on a different node within the distributedsystem. In one embodiment of the invention, the node corresponds to adistinct computing device. Alternatively, the node may correspond to acomputer processor with associated physical memory. The node mayalternatively correspond to a computer processor or micro-core of acomputer processor with shared memory and/or resources.

While FIG. 1 shows a configuration of components, other configurationsmay be used without departing from the scope of the invention. Forexample, various components may be combined to create a singlecomponent. As another example, the functionality performed by a singlecomponent may be performed by two or more components.

FIG. 2.1 is an example portion of a sensing region (200) in accordancewith one or more embodiments of the invention. The example in FIG. 2.1is for explanatory purposes only and not intended to limit the scope ofthe invention. For example, the dimensions of the sensing region,dimensions and positioning of electrodes, type sensing region, as wellas any other aspects of FIG. 2.1 may change without departing from thescope of the invention. Further, the use of variables in FIG. 2.1 is todistinguish different components of the same or similar type from eachother.

In FIG. 2.1, the portion of the sensing region (200) includestransmitter electrode X (202) and transmitter electrode Y (204).Transmitter electrode X (202) and transmitter electrode Y (204) may bedriven concurrently with transmitter signals (e.g., transmitter signal X(206), transmitter signal Y (208)). In other words, the transmittersignals are sent at least at partially overlapping times. In someembodiments, the transmitter signals are sent at the same time orsubstantially the same time. Receiver electrodes (e.g., receiverelectrode M (210), receiver electrode N (212)) receive resulting signalsthat include the effects of the transmitter signals. More particular,the resulting signals include the effects of the transmitter signals,noise, and any change in capacitance at an intersection of thetransmitter electrode and the receiver electrode, such as caused by aninput object.

In one or more embodiments of the invention, because the transmitterelectrodes are driven concurrently, the resulting signal received by areceiver electrode includes effects of both the transmitter signals onthe transmitter electrodes. For example, receiver electrode M (210)receives a resulting signal that includes the effects of transmittersignal X (206), transmitter signal Y (208), noise, and any input objectspresent in the example portion of the sensing region (200).

Continuing with FIG. 2.1, the transmitter signal is generated bymodulating a carrier signal (e.g., S(t) (214)) based on a respectivedigital code (e.g., digital code_(x)(t) (216), digital code_(y)(t)(218)). In the example of FIG. 2.1, “t” refers to time. A carrier signalis a transmitted wave at a steady base frequency of alternation. In oneor more embodiments, the frequency and the amplitude of the carriersignal is consistent over time t. For example, the carrier signal may bea square wave, a sine wave, a cosine wave, or other such periodicsignal.

The digital code is a code having multiple sequential elements, wherebyeach sequential element defines a particular modulation (denoted as acircle with an X in FIG. 2.1) of the carrier signal for a correspondingperiod of time. In other words, each element defines a variation on thecarrier signal for the corresponding period of time to create thetransmitter signal. The variation may be a pre-emphasis boost, a changein amplitude, a change in phase, a change in frequency, a change in anumber of pulses per period time or another change. In one or moreembodiments, at least one of the elements of the digital code is anon-integer multiple. A non-integer multiple is a value in the digitalcode that causes an element in the digital code to exist that isnon-integer after any scaling is performed to make the smallestmagnitude of an element to be one. In other words, when the digital codeis scaled so that the smallest magnitude of an element is one, anon-integer value is in the digital code. The scaling is performed bymultiplying each element by the same value. One way to determine whethera digital code includes a non-integer multiple is to scale the digitalcode by a same value so that the absolute value of at least one elementis 1 and the absolute values of any remaining elements are greaterthan 1. If the resulting digital code (i.e., the digital code thatresults from performing the scaling) includes a non-integer value, thenthe digital code includes a non-integer multiple. The digital code mayfurther include elements that are negative multiples, positivemultiples, integer multiples, and other values. The sequence of elementsdefines a sequence of variations of the carrier signal over the span ofperiods of time.

Each transmitter electrode that transmits concurrently has acorresponding unique digital code for a concurrent transmission oftransmitter electrodes. The digital code assigned to a transmitterelectrode may change for another concurrent transmission. The digitalcode assigned to a transmitter electrode may be a circular shift of thedigital code assigned to another transmitter electrode. In one or moreembodiments of the invention, the digital codes assigned to thetransmitter electrodes are orthogonal. By being orthogonal, the digitalcodes exhibit a higher SNR than non-orthogonal digital codes. SNR may bedescribed by gain ‘g’, where the gain of 1 corresponds to non-codedivision multiplexing excitation (i.e., both the convolution matrix Cand the deconvolution matric D are simply identity matrix with elementof ones diagonally and zeros elsewhere). That is, when the convolutionand deconvolution matrices are both an identity matrix, then thetransmitter electrodes are not transmitting concurrently, but rathertransmitting sequentially. Mathematically, D*C=I*I=I. Using CDM4 as anexample, the gain is 4, so SNR is 4 times higher than non-code divisionmultiplexing excitation, or D*C=4I.

Although FIG. 2.1 shows only two transmitter electrodes, the sensingregion may have more than two transmitter electrodes. In accordance withone or more embodiments of the invention, the number of transmitterelectrodes is greater than or equal to the number of elements in thedigital codes. If the number of transmitter electrodes is greater thanthe number of elements of the digital codes, then the number oftransmitter electrodes transmitting concurrently is less than the numberof elements of the digital codes.

Although FIG. 2.1 shows a particular diagram of a sensing region inwhich transmitter electrodes span a length of the sensing region and areorthogonal to the sensing region, other layouts of electrodes may beused. For example, as described above with reference to FIG. 1, sensorelectrodes may be arranged in a grid pattern, wherein each node in thegrid is a separate electrode. FIG. 2.2 shows an example portion of asensing region (250) with sensor electrodes (e.g., sensor electrode Q(252), sensor electrode R (254), sensor electrode S (256)) arranged in agrid pattern. In the grid pattern, the sensor electrodes may function astransmitter electrodes and receiver electrodes for different periods oftime. For example, during a first time period, sensor electrode Q (252)and sensor electrode S (256) may be transmitter electrodes, and sensorelectrode R (254) may be a receiver electrode. During another period oftime, sensor electrode R (254) may be a transmitter electrode, andsensor electrode Q (252) and sensor electrode S (256) may be receiverelectrodes. In the example, when sensor electrode Q (252) and sensorelectrode S (256) are transmitting concurrently, sensor electrode Q(252) and sensor electrode S (256) may each be driven with a transmittersignal that is obtained by modulating a carrier signal using a digitalcode assigned to the sensor electrode. As described above with referenceto FIG. 2.1, the digital code includes at least one non-integer value.Thus, the resulting signal received by the receiver sensor electrode maybe demodulated to partition the effects of an input object in differentpositions of the sensing region.

Further, in one or more embodiments of the invention, the carrier signalfrequency may be higher than the rate of the digital code. For example,the frequency of the carrier signal may be higher than the rate at whichthe digital code modulates the carrier signal. Other embodiments mayexist without departing from the scope of the invention.

FIG. 3 shows a table with example digital codes in accordance with oneor more embodiments of the invention. In the example of FIG. 3, thefirst column (302) is a row identifier, the second column (304) is aname of a pseudo noise sequence that may be used as a digital code, thethird column (306) shows the digital code for the correspondingtransmitter electrode, the fourth column (308) shows a deconvolutionpattern to deconvolve the resulting signal by a receiver electrode, andthe fifth column shows the resulting gain.

In the example, the third column (306) shows example digital codes,whereby each digital code includes multiple elements and each element isa number in the digital code. The transmitter signal for the firsttransmitter electrode is based on a digital code in a particular row aspresented in the third column. The transmitter signal for the secondtransmitter electrode is based on the digital code in the third columnand the particular row, but with a circular shift by one. In otherwords, the second transmitter electrode is driven based on a digitalcode starting on the second element and ending on the first element.Similar shifting may be performed for the remaining transmitterelectrodes that transmit concurrently.

Continuing with the example, the normalized deconvolution column showshow the resulting signal may be de-convolved to identify the transmittersignal being affected by an input object in the sensing region. Thedeconvolution is performed over the span of time of the transmissionsignals.

In the example, each row is for a particular pseudo noise sequence. Row1 (312), row 2 (314), row 4 (318), row 6 (322), row 8 (326), and row 10(330) show existing pseudo noise sequences. Row 3 (316), row 5 (320),row 7 (324), row 9 (328), and row 11 (332) show the existing pseudonoise sequences modified to include non-integer multiples. For example,as shown in Row 3 (316), the Barker₁₁, non-integer multiple, replaceseach “1” in standard Barker₁₁ (shown in Row 2 (314)) with a “0.634”. Byusing a non-integer multiple, instead of a gain of 6 as with standardBarker₁₁, a gain of 8 is achieved as shown in the fifth column (310).Similar consequences of greater gain are achieved using non-integermultiples as compared to the standard counterparts. Further, by usingnon-integer multiples, the digital codes are orthogonal in accordancewith one or more embodiments of the invention. The fact that the digitalcodes are orthogonal means that the resulting signal has optimal signalto noise ratio. In other words, the resulting signal has less artifactsof noise and includes greater effects of any input objects in thesensing region.

Additionally, in the example of Lengedre17 in Row 10 (330), becauseLengedre17 is not invertible, Lengedre17 may not be used as a digitalcode. In other words, deconvolution of the resulting signal may not beperformed. However, the non-integer multiple version in Row 11 isinvertible. Thus, the non-integer multiple provides a digital code thatmay be used to concurrently drive 17 transmitter electrodes. By beingable to concurrently drive 17 transmitter electrodes, the sametransmitter electrode may obtain more measurements of the sensing regionmay be acquired over the same time period as using time slicing inaccordance with one or more embodiments of the invention. In otherwords, more time may be allocated to each transmitter electrode toobtain measurements because the time may overlap with 16 othertransmitter electrodes. The additional measurements may be achieved byincreasing the number of pulses and obtaining more resulting signals. Inone or more embodiments of the invention, concurrently driving 17transmitter electrodes may allow for less time to perform a frame ofsensing. In other words, more sensing frames may be obtained for thesame time period. Thus, the input device may be more responsive to theexistence and movement of input objects in the sensing region.

FIG. 4 shows a flowchart in accordance with one or more embodiments ofthe invention. While the various steps in this flowchart are presentedand described sequentially, one of ordinary skill will appreciate thatsome or all of the steps may be executed in different orders, may becombined or omitted, and some or all of the steps may be executed inparallel.

In Step 401, digital codes having at least one non-integer multiple areselected in accordance with one or more embodiments of the invention. Inone or more embodiments of the invention, the digital codes are selectedbased on the number of transmitter electrodes to be concurrentlytransmitting. The number of elements in the digital code is at least thesame as the number of transmitter electrodes. Further, in accordancewith one or more embodiments of the invention, the amount of gain andefficiency of digital code may be used as a factor in selecting digitalcodes.

In Step 403, the transmitter electrodes are driven concurrently withtransmitter signals, the transmitter signals based on the digital codeshaving the non-integer multiples. In one or more embodiments, a carriersignal for a transmitter electrode is modulated using the elements ofthe digital code. In other words, each element in the digital codeassigned to the transmitter electrode modulates the carrier signal insequential order of the digital code. The modulation may be to multiplythe amplitude of the carrier signal by the amount of the current elementin the digital code. By way of another example, the voltage of thecarrier signal may be changed according the digital code. In otherwords, where a non-integer multiple is the current element, the voltageof the transmitter signal may be a fraction of the voltage of thecarrier signal. By way of another example, the number of pulses of thecarrier signal may be changed based on the current element in thedigital code. Specifically, for each element, the number of pulses forthe time period allocated to the element is changed based on theelement. In the example, for Barker₁₁, the first three transmitterelectrodes may be driven with 634 pulses in positive polarities and thenext three transmitter electrodes may be driven with 1000 pulses innegative polarities. By way of another example, pre-emphasis boost maybe used to modulate the carrier signal. In other words, for an initialphase of the signal, the carrier signal is excited at a higher level.For a later phase, the signal drops to a lower level. The length of timeand/or the magnitude of the higher level and the lower level is definedsuch the average is a function of the current element in the digitalcode.

As discussed above, each element in the digital code is allocated a timeperiod according to the order in the digital code. When each element inthe digital code is processed, the driving of the transmitter electrodesmay be complete. In some embodiments, the next set of transmitterelectrodes that transmit concurrently is processed.

As the transmitter electrodes are driven, resulting signals that arebased on the transmitter signals are received in Step 405. The resultingsignals include effects of the transmitter signals, noise, and any inputobject in the sensing region. For example, for a particular transmitterelectrode, the transmitter signal is affected by the capacitive couplingbetween the transmitter electrode and the receiver electrode as well asthe capacitive changes caused by the presence of an input object wherethe transmitter electrode is capacitively coupled to the receiverelectrode. The foregoing result is further combined with the results ofeach transmitter signals of transmitter electrodes that are capacitivelycoupled to the same receiver electrode. Thus, if an input object ispresent, the resulting signals is an amalgamation of the transmittersignals including at least one transmitter signal being affected by thepresence of the input object. The resulting signals may span the timeperiods in which the elements of the digital codes are processed.

In Step 407, positional information is determined from the resultingsignals in accordance with one or more embodiments of the invention.Measurements of the resulting signals are obtained. Deconvolution isperformed on the measurements to obtain measurements corresponding toeach transmitter electrode that transmitted concurrently. By way of anexample, if the convolution matrix is Cn, the deconvolution matrix Dn issimply an inverse of Cn (i.e., Dn=Cn⁻¹). If the matrix of Cn iscirculant (e.g., the digital codes assigned to the transmitterelectrodes are circular shifted) and is also orthogonal, then the rowsof Cn is equal to the columns of Dn. Thus, Dn is the transpose of Cn(i.e., Dn=Cn^(T)).

From the measurements, a baseline of the sensing region that removes thepresence of noise may be subtracted. The results may be combined into acapacitive image of the sensing region, which has peak measurementvalues at locations in which the input object is present. The locationsof the input objects, size, shape, and other information may be obtainedfrom the capacitive image as positional information. The positionalinformation may be reported to a host device, and used to perform a userinterface or other action.

While the invention has been described with respect to a limited numberof embodiments, those skilled in the art, having benefit of thisdisclosure, will appreciate that other embodiments can be devised whichdo not depart from the scope of the invention as disclosed herein.Accordingly, the scope of the invention should be limited only by theattached claims.

What is claimed is:
 1. A capacitive sensing device comprising: a firsttransmitter electrode, a second transmitter electrode, and a pluralityof receiver electrodes; and a processing system configured to:concurrently drive a first transmitter electrode with a firsttransmitter signal and a second transmitter electrode with a secondtransmitter signal, wherein the first transmitter signal is based on afirst digital code and the second transmitter signal is based on asecond digital code, and wherein the first digital code and the seconddigital code each comprise at least one non-integer multiple, receive aplurality of resulting signals using a plurality of receiver electrodes,the plurality of resulting signals comprising effects of the firsttransmitter signal and the second transmitter signal, and determinepositional information based on the plurality of resulting signals. 2.The capacitive sensing device of claim 1, wherein the first digital codeand the second digital code are orthogonal.
 3. The capacitive sensingdevice of claim 1, wherein the first digital code comprises a negativevalue, the negative value reflected in the polarity of the firsttransmitter signal.
 4. The capacitive sensing device of claim 1, whereinconcurrently driving the first transmitter electrode and the secondtransmitter electrode comprises performing pre-emphasis based on the atleast one non-integer multiple in the first digital code and the seconddigital code.
 5. The capacitive sensing device of claim 1, wherein thefirst digital code is a circular shift of the second digital code. 6.The capacitive sensing device of claim 1, wherein the first digital codecomprises a plurality of elements, each element of the plurality ofelements defining a voltage that is used to drive the first transmitterelectrode.
 7. The capacitive sensing device of claim 1, wherein thefirst digital code comprises a plurality of elements, each element ofthe plurality of elements defining a number of pulses at each period oftime when driving the first transmitter electrode.
 8. The capacitivesensing device of claim 1, wherein the first digital code furthercomprises at least one selected from a group consisting of a negativemultiple and an integer multiple.
 9. The capacitive sensing device ofclaim 1, wherein the first digital code comprises at least one selectedfrom the group consisting of: [0.634 0.634 0.634 −1 −1 −1 0.634 −1 −10.634 −1], [0.789 0.789 0.789 0.789 0.789 −1 −1 0.789 0.789 −1 0.789 −10.789], [−1 0.466 1 0.466 0.936 1 1 −1 −1 0.466 0.936 −1 0.936], [1 −⅔ 11 −⅔ −⅔ 1 −⅔ −⅔ −⅔ 1 1 1 1 −⅔], and [0.195 1 1 −0.61 1 −0.61 −0.61 −0.611 1 −0.61 −0.61 −0.61 1 −0.61 1 1].
 10. The capacitive sensing device ofclaim 1, wherein the first transmitter signal is based on the firstdigital code comprises modulating a carrier signal based on firstdigital code and the second transmitter signal is based on the seconddigital code comprises modulating the carrier signal based on the seconddigital code.
 11. The capacitive sensing device of claim 10, wherein thecarrier signal comprises a varying voltage.
 12. A method for capacitivesensing comprising: concurrently driving a first transmitter electrodewith a first transmitter signal and a second transmitter electrode witha second transmitter signal, wherein the first transmitter signal isbased on a first digital code and the second transmitter signal is basedon a second digital code, and wherein the first digital code and thesecond digital code each comprise at least one non-integer multiple;receiving a plurality of resulting signals using a plurality of receiverelectrodes, the plurality of resulting signals comprising effects of thefirst transmitter signal and the second transmitter signal; anddetermining positional information based on the plurality of resultingsignals.
 13. The method of claim 12, wherein concurrently driving thefirst transmitter electrode and the second transmitter electrodecomprises performing pre-emphasis based on the at least one non-integermultiple in the first digital code and the second digital code.
 14. Themethod of claim 12, wherein the first digital code comprises a pluralityof elements, each element of the plurality of elements defining avoltage that is used to drive the first transmitter electrode.
 15. Themethod of claim 12, wherein the first digital code comprises a pluralityof elements, each element of the plurality of elements defining a numberof pulses at each period of time when driving the first transmitterelectrode.
 16. The method of claim 12, wherein the first digital codefurther comprises at least one selected from a group consisting of anegative multiple and an integer multiple.
 17. The method of claim 12,wherein the first transmitter signal is based on the first digital codecomprises modulating a carrier signal based on first digital code andthe second transmitter signal is based on the second digital codecomprises modulating the carrier signal based on the second digitalcode.
 18. A processing system for capacitive sensing comprising: sensorcircuitry configured to: concurrently drive a first transmitterelectrode with a first transmitter signal and a second transmitterelectrode with a second transmitter signal, wherein the firsttransmitter signal is based on a first digital code and the secondtransmitter signal is based on a second digital code, and wherein thefirst digital code and the second digital code each comprise at leastone non-integer multiple, and receive a plurality of resulting signalsusing a plurality of receiver electrodes, the plurality of resultingsignals comprising effects of the first transmitter signal and thesecond transmitter signal; and processing circuitry configured to:determine positional information based on the plurality of resultingsignals.
 19. The processing system of claim 18, wherein the firstdigital code comprises a plurality of elements, each element of theplurality of elements defining a voltage that is used to drive the firsttransmitter electrode.
 20. The processing system of claim 18, whereinthe first digital code comprises a plurality of elements, each elementof the plurality of elements defining a number of pulses at each periodof time when driving the first transmitter electrode.